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Auto merge of rust-lang#74839 - alarsyo:multiple_return_terminators, …
…r=oli-obk Implement multiple return terminator optimization Closes rust-lang#72022
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38 changes: 38 additions & 0 deletions
38
compiler/rustc_mir/src/transform/multiple_return_terminators.rs
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,38 @@ | ||
| //! This pass removes jumps to basic blocks containing only a return, and replaces them with a | ||
| //! return instead. | ||
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| use crate::transform::{simplify, MirPass, MirSource}; | ||
| use rustc_index::bit_set::BitSet; | ||
| use rustc_middle::mir::*; | ||
| use rustc_middle::ty::TyCtxt; | ||
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| pub struct MultipleReturnTerminators; | ||
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| impl<'tcx> MirPass<'tcx> for MultipleReturnTerminators { | ||
| fn run_pass(&self, tcx: TyCtxt<'tcx>, _: MirSource<'tcx>, body: &mut Body<'tcx>) { | ||
| if tcx.sess.opts.debugging_opts.mir_opt_level < 3 { | ||
| return; | ||
| } | ||
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| // find basic blocks with no statement and a return terminator | ||
| let mut bbs_simple_returns = BitSet::new_empty(body.basic_blocks().len()); | ||
| let bbs = body.basic_blocks_mut(); | ||
| for idx in bbs.indices() { | ||
| if bbs[idx].statements.is_empty() | ||
| && bbs[idx].terminator().kind == TerminatorKind::Return | ||
| { | ||
| bbs_simple_returns.insert(idx); | ||
| } | ||
| } | ||
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| for bb in bbs { | ||
| if let TerminatorKind::Goto { target } = bb.terminator().kind { | ||
| if bbs_simple_returns.contains(target) { | ||
| bb.terminator_mut().kind = TerminatorKind::Return; | ||
| } | ||
| } | ||
| } | ||
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| simplify::remove_dead_blocks(body) | ||
| } | ||
| } |
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